ACTION OF THE HALOGENS^ ETC. 167 



Nitrogen Determination. 



.1685 grms. substance gave at 746.7 m. m. and 29° 13.1 c. c. of N. 



Computed: Found: 



N=8.04%. 8.27%. 



Paratoluthiochinanthrene gives beautifully crystallizing salts 

 with the mineral acids and with picric acid. The sulphuric acid salt 

 crystallizes in two modifications, one anhydrous, gleaming yellow 

 needles, the other containing water of crystallization, scarlet needles. 

 The yellow variety is the unstable one. It separates out first from 

 the solution and changes slowly on standing, or suddenly on filter- 

 ing, into the scarlet variety. The scarlet variety loses two molecules 

 of water on standing over sulphuric acid in a desiccator, and passes 

 over into the yellow form. This yellow variety changes back to the 

 scarlet by standing in the air or by being pressed by any hard object. 

 This last phenomenon is explained by the fact that it is impossible 

 to remove the last traces of sulphuric acid from the crystals (one 

 can not wash them with water, since they then separate into base and 

 acid); therefore there remains a little somewhat diluted sulphuric 

 acid on the crystals after they are dried in the desiccator. By 

 suddenly pressing the crystals they take this water on from the acid 

 in the form of water of crystallization and thus pass over into the 

 scarlet modification. The hydrochloric acid salt of the correspond- 

 ing base from orthotoluquinoline shows the same phenomenon, 

 except that in this case the colors are reversed, in that the yellow 

 salt contains water and the scarlet one is anhydrous. 



All of these salts are decomposed by heating with water. 



Nitric Acid Salt. 



By dissolving the base in concentrated nitric acid, one obtains, 

 when the solution cools, long, golden needles, which contain four 

 molecules of nitric acid. The nitric acid was determined not only 

 by titration with standard Ba(0H)2 solution but also by means of a 

 nitrogen determination (Dumas). 



